The present invention relates to a color filter which is obtained by coloring a picture element part with an ink jet system and which is suitable for a color liquid crystal display and a process for producing the same.
Recently, there has been a tendency that a demand for a liquid crystal display, particularly a color liquid crystal display is increasing with the development of a personal computer, particularly a portable personal computer. However, since this color liquid crystal display is expensive, a demand for the cost-cut is getting higher and, in particular, a demand for the cost-cut of a color filter weighing in a respect of cost is high.
In such a color filter, a liquid crystal usually operates as a shutter by equipping with three primary colors of red (R), green (G) and blue (B) and switching ON and OFF of an electrode corresponding to each picture element part of R, G and B and the color display is performed by transmission of the light through each picture element part of R, G and B.
As a process for producing a color filter which has hitherto been carried out, there is, for example, a dyeing process. In this dyeing process, a water-soluble polymer material which is a material for dyeing is first formed on a glass substrate, which is patterned into the desired shape by a photolithography step and the resulting pattern is dipped into a dyeing bath to obtain a colored pattern. This is repeated three times to form a color filter layer consisting of picture element parts of R, G and B.
Alternatively, as an another method, there is a pigment dispersing method (color resist method). In this method, a photosensitive resin layer in which a pigment is dispersed is first formed on a substrate and this is subjected to patterning to obtain a monocolor pattern. Further, this step is repeated three times to form a color filter layer consist of picture element parts of R, G and B.
As a still another method, there are an electrode position method and a method of dispersing a pigment in a thermosetting resin and performing three times printing of R, G and B and, thereafter, thermally curing the resin. However, in any method, the same step needs to be repeated three times for coloring three colors of R, G and B, and there is a problem that the cost is high and a yield is decreased because of repetition of a step.
As a process for producing a color filter which has solved these problems, there is proposed a method of blowing a coloring ink with an ink jet system to form a colored layer (picture element part) (JP-A-59-75205). In the publication, there are disclosed a method in which a convex part which is a border is printed in advance with a material having the worse wettability on an ink when an ink having the better wettability on a glass substrate is used, and a method in which a pattern is formed in advance with a material having the better wettability on an ink to help the ink fixation when an ink having the worse wettability on a glass is used. However, there is no description regarding how to specifically coat a material having the better wettability and a material having the worse wettability.
On the other hand, as another process for producing a color filter by blowing a coloring ink by an ink jet system to form a colored layer (picture element part), there is disclosed a method of treating a concave part with an inkphilic treating agent in JP-A-9-203803. In this method, a convex part is formed in advance on a substrate and this convex part is made to be ink-repellent and, thereafter, the whole substrate is surface-treated with the inkphilic treating agent. However, in this method, since a convex part needs to be ink-repellent in advance upon the inkphilic treatment, there is a problem that two times treatments of the ink-repulsion treatment and the inkphilic treatment need to be performed.
In addition, as a method for producing a color filter by forming a colored layer with an ink jet system, there is described a method of forming a colored layer (picture element part) by providing an ink absorbing layer on a substrate and making a difference in the ink absorbability of this absorbing layer between an exposed part and an unexposed part in JP-A-8-230314 and JP-A-8-227012. However, in this method, since a colored layer is formed by forming an absorbing layer and absorbing an ink in this absorbing layer, there is a problem that a difference in the coloration between a central part of an ink dot and a surrounding part of that is present which results in the color nonuniformity. In addition, there is also a problem that this absorbing layer needs the predetermined thickness resulted from its function of absorbing an ink.
The present invention was done in view of the above problems and a main object thereof is to provide a color filter in which a part having the better wettability and a part having the worse wettability can be formed on a single layer regarding the wettability of a substrate which becomes problematic upon formation of a picture element part with an ink jet system, and a pattern formed of the part having the better wettability and the part having the worse,wettability can be formed in a few steps and, further, an ink absorbing layer is not necessary, and which has the better quality and which can be produced with the low cost, and a process for producing the same.